We are planning to study the nature of cell junctions between melanocytes and keratinocytes in freeze-fracture studies in order to find out whether there is any special relationship between melanocytes and keratinocytes. We also plan to carry on with our studies on the formation of melanosomes in retinal pigment cells in vitro, with special reference to a possible role of ultraviolet. Finally, we are planning to carry on with our investigation on the comparative histology of the epidermal melanocyte system of primates. In another line of investigation, we plan to find evidence for the role of singlet oxygen in melanogenesis using known quenchers of singlet oxygen, and to find out whether our preliminary data indicate an active role of singlet oxygen or whether DABCO interferes with the histochemical Dopa reaction by some other so far unknown mechanism. The effect of ultraviolet and carcinogens, with special reference to the role of psoralen in light sensitization will be carried out as well. BIBLIOGRAPHIC REFERENCES: Pathak, M.A., Jimbow, K., Szabo, G. and Fitzpatrick, T.B.: Sunlight and melanin pigmentation. In: Photochemical and Photobiological Reviews, K. Smith, ed., Plenum Press, New York, pp. 211-239, 1976. Rosdahl, I. and Szabo, G.: Thymidine labelling of epidermal melanocytes in uv irradiated skin. Acta Derm. Venereol. 56:159-162, 1976.